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Lichens of Arkansas

Lichens of Arkansas

The next time you take a walk through your neighborhood,  take a look around you.  Have you noticed those crusty patches of colors growing on the trees, on the rock walls, or on old buildings downtown?    Those are small plantlike organisms known as lichens.  That unusually small living organism contributes to our natural world.

Lichens have traditionally been referred to as prime examples of symbiotic relationships.  A fungus and an algae successfully form an alliance to produce a spongy body that is called a thallus.  The fungus protects the algae from physical injury by environmental forces, and the algae supplies the food for both organisms. Pigments produced by the fungus supply the rich range of colors found in lichens.

There are three growth forms that occur in lichens: crustose lichens, which look like a thin crust and  can be found on the surfaces of walls or tree bark; foliose lichens,  which are leaf-like and grow on the surface of rocks or stones; and fruticose lichens, which are erect or pendent. Lichens grow very slowly, at the maximum rate of 1 centimeter per year  and at the minimum rate of 0.1 millimeter per year. They are capable of living to an age of more than 4,500 years.  They can withstand extreme temperatures from -198 degrees C to 50 degrees C, and tolerate environmental conditions that kill most other lifeforms. There are around 30,000 species of lichen throughout the world . They grow on bare surfaces  of exposed desert rock or to the frozen surface of the polar regions. In addition, they often form colorful, crusty patches on the rock surfaces of mountain tops and along  coastal boulders in intertidal zones.  One species grows completely submerged on ocean rocks. The forest floors supply the tree bark and branches for prime growth areas of lichen. Some tropical hardwood trees contain lichen growing just beneath the cuticle of their leaves. Lichens even attach themselves to man-made substances such as concrete, glass, asbestos, and iron grave markers.  

Lichens provide food for many animals. Reindeer and caribou consume fruticose lichens in the Lapland and North African sheep graze on crustose lichen. Cladonia rangiferina are eaten by many arctic animals and sometimes by people. Lecanora, a desert lichen, is collected and eaten in Libya. The desert tribes grind Lecanora, the manna of the Israelites, into a substance used to make bread.  Iceland Moss is cooked into a  rich gelatinous substance that is very digestible and produces a soup for invalids.

Equally important was the use of lichens in the dye process.  Blue dye was especially favored by the North American Indians of Oklahoma.  The ancient worlds of the Greeks and Hebrews preferred the rich    purple and blue hues. The Scots used lichen to produce their famous Scottish "tweeds".   Orchil producing  lichens supplied  food colouring agents.  Using lichen extracts, the Europeans created scents  for perfumes and soaps.   Elementary chemistry labs have used litmus paper for an acid/alkaline test.  Moreover, the use of lichens by model toy makers was unique.  Because fructose lichens resembled miniature shrubs and trees, they were incorporated into model railroad and car tracks.

There were beliefs that lichens could be used in medicines. In fact, antibiotic properties have been  found in many lichens.  Europeans, at one time, used a mixture of these properties to treat tuberculosis, minor cuts and abrasions, and skin diseases. Lungwort was believed to cure chest problems, and Old Man’s Beard was a cure for hair loss.

In the past, the study of lichens had been neglected. But in recent years, careful studies have produced  a clearer understanding of these organisms. More importantly, lichens are being used as indicators of air pollution because of their sensitivity to sulfur dioxide and other gaseous pollutants.

Lichens are unusual and yet beautiful organisms. They are known as the pioneers of the plant world  and have played an important role in transforming barren land into colorful fields, woodlands, and  rocky surfaces.  More recently, lichens are being recognized as a barometer for our "healthy natural environment. Many examples of lichens can be found throughout the many regions of Arkansas. From the rocky surfaces of Petit Jean Mountain to the forests of the Ouachita River, lichens can be seen growing. They are truly one of natures most unnoticed and at- tractive organisms.

Project Author: Donna Heaberlin

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